The present invention is generally related to DC-DC converter technology. More particularly, the present invention provides methods and circuits for current control circuits that can be used in a DC-DC converter and other applications.
A DC-to-DC converter is a circuit for converting a direct current (DC) from one voltage level to another. It is a class of power converter. Linear regulators can only output at lower voltages from the input. Switch-mode DC to DC converters convert one DC voltage level to another, by storing the input energy temporarily and then releasing that energy to the output at a different voltage. Switch-mode DC to DC converters can convert an input voltage to a lower or higher output voltage, and they are more efficient than the linear regulators.
A DC-DC converter often includes a current sense circuit for providing a current sense signal as a feedback signal representing a current flow in the inductive coil. The current sense signal is compared with a reference signal for controlling the operation of the converter. A slope compensation circuit is often provided in conventional current-mode controlled DC-DC converters. The output of the slope compensation circuit is used for changing the slope at which a reference signal intersects with a current sense signal. Thus, the slope compensation circuit outputs a slope compensation signal superimposed on the current sense signal, which is used as a control parameter.
In some convention converters, the slope compensation signal is often formed by transforming an oscillation signal and then superimposing it on the current sense signal. However, the oscillation signal is referenced to a ground signal when being generated.
Even though conventional slope compensation circuits have been used to maintain stability of DC-DC converters, they often have limitations. Some of the limitations are described below in more details. Therefore, improved techniques for providing slope compensation signals are highly desirable.